Otherwise your terminal may be missing true-color terminal mode or the mpv in your distro doesn't have that output plugin. (You can check with "mpv --vo=help")
You need to edit spongebob-cli to add the arguments to the code where it calls mpv. It sounds like you're just running it and providing the arguments to its prompt.
I enter spongebob-cli
Then when it prompts me to enter an episode number, I can't seem to get it to play from within the terminal itself
let's say I want to play episode 1:
1 --mpv --vo=tct --quiet
Doesn't seem to work. Any help to get past this would be greatly appreciated